Solid composite propellants with salts of ferrocene monosulfonic acid as burning rate modifiers

ABSTRACT

1. A solid propellant composition based on a polymer selected from the group consisting of hydrocarbon, polysulfide and urethane polymers and comprising, as a burning rate modifier component thereof, approximately 1 to 3 percent by weight of said composition of at least one salt of ferrocene monosulfonic acid which is less volatile than ferrocene.

United States Patent Inventor Stephen W. Osborn Yardley, Pa.

Appl. No. 145,538

Filed Oct. 13, I961 Patented Sept. 21, 1971 Assignee Thiokol Chemical Corporation Bristol, Pa.

SOLID COMPOSITE PROPELLANTS WITH SALTS OF FERROCENE MONOSULFONIC ACID AS BURNING RATE MODIFIERS 22 Claims, No Drawings US. Cl 149/19, 149/83, 149/109 Int. Cl C06d 5/00, C101 9/10 Field of Search 149/17, l8,

[56] References Cited UNITED STATES PATENTS 3,038,300 6/1962 Pedersen 149/109 X 3,038,299 6/1962 Pedersen 60/35.4 3,002,830 10/1961 Barr 149/19 Primary Examiner-Benjamin R. Padgett Alt0rney-Thomas W. Brennan SOLID COMPOSITE PROPELLANTS WI'III SALTS OF FERROCENE MONOSULFONIC ACID AS BURNING RATE MODIFIERS This invention relates to the use of nonvolatile salts of ferrocene monosulfonic acid as burning rate controlling agents in solid propellant compositions. In particular, this invention relates to the use of such salts as the ammonium, sodium, ferrous, potassium, calcium, strontium and barium ferrocene sulfonatcs as nonmigrating, burning rate controlling agents in solid propellant compositions.

Fcrrocene, dicyclopentadienal iron, has been reported as a burning rate modifying agent in the combustion or oxidation of fuels. The use of ferrocene in solid propellant compositions for this purpose, however, imposes difficulties where storage of the solid propellant composition is required over protracted periods of time. The ferrocene component of these solid admix propellant compositions, due to its subliming nature, will set up concentration gradients within the body of the admix upon storage even at ambient temperature and ultimately will migrate to the surface of such compositions. In time, crystalline ferrocene will form on the surface of such compositions. The unequal distribution of this burning rate modifier constituent in the body of the propellant mix produced by this migration phenomenon will provide for nonuniform burning properties in the body of the propellant being oxidized and thereby detract from the reliability and utility of stored propellant compositions containing ferrocene.

It has now been unexpectedly found according to the present invention that a nonvolatile salt of ferrocene monosulfonic acid and in particular the ammonium, sodium and ferrous salts of ferrocene monosulfonic acid, will act as a nonmigrating burning rate control agent in solid propellant compositions and that the modification of the burning rate of the propellant compositions obtained with these novel burning rate modifiers is substantially superior to that obtained using ferrocene. In respect to the present invention the term modification of the burning rate means an acceleration of the burning rate. Other nonvolatile salts that may be used within the concept of the present invention are the potassium, calcium, strontium and barium salts of ferrocene monosulfonic acid. By nonvolatile it is meant that the salt is less volatile than ferrocene at room temperature. Under the relatively prolonged storage conditions common to the solid propellant rocket field no concentration gradients of the novel burning rate modifiers of the present invention occurs in solid propellant compositions made therewith due to the migration phenomenon. Propellant compositions and solid fueled rockets made therewith and containing these novel burning rate modifiers can be stored for relatively long periods of time under relatively extreme temperature conditions, i.e., approximately 50 C. to +100 C., without any migration of these novel burning rate modifiers occurring.

The novel burning rate modifiers of the present invention can be used with various types of solid propellant compositions based on various polymeric materials including hydrocarbon type polymers such as copolymers of butadiene and acrylic acid; urethane polymers and polysulfide type polymers such as LP-3 and LP-33 polymers sold by Thiokol Chemical Corporation. Where the propellant composition is based on a carboxyl containing hydrocarbon polymer the preferred burning rate modifier according to the present invention is ammonium ferrocene monosulfonate.

To impart the desired burning rate properties to the propellant composition approximately lto 3 parts by weight of one or more of the novel burning rate modifiers of the present invention are used per 100 parts by weight of the total propellant composition. In use, the novel burning rate modifiers of the present invention are incorporated, that is, uniformly admixed, into the solid propellant composition admixes.

Because of the substantially improved burning rate properties of the novel burning rate modifiers of the present invention substantially less of these materials is required than would be needed of ferrocene to achieve the same results.

The preparation of ammonium ferrocene monosulfonate is described by V. Weinmayr. .l. A.C.S., 77, 3009, 1955 and Knox and Pauson, J. A.C.S. 692, I958. Sodium ferrocene monosulfonate may be prepared by dissolving ammonium ferrocene monosulfonate in water or methanol and crystallizing out sodium ferrocene monosulfonate with sodium chloride. Ferrous ammonium monosulfonate may be prepared by dissolving ammonium ferroccne monosulfonate in water or methanol and crystallizing out ferrous ferrocene monosulfonate with ferrous ammonium sulfate. The preparation of the potassium, calcium, strontium and barium salts can be made in a similar fashion from ammonium ferrocene monosulfonate using respectively such salts as potassium chloride, calcium chloride, strontium nitrate and barium chloride.

The following examples are merely illustrative of the scope of the present invention and are not intcndedras a limitation thereof.

EXAMPLE I This example illustrates the burning rates, Rb, given in inches per second, which are obtained when several of the novel burning rate modifiers of the present invention are each used in a propellant composition. Strand burning test procedures were used to test the formulations. For comparison purposes, tests were also run with the same propellant composition formulation using no burning rate modifying agent as well as using ferrocene as a burning rate modifying agent. The formulations used and the results obtained are as follows:

When propellant compositions of the type disclosed in this example are stored at approximately 50 C. to +l00 C. for relatively long periods of time no migration of the novel burning rate modifiers of the present invention occurs.

EXAMPLE 2 The change in burning rate arising due to the use of iron ferrocene monosulfonate as a burning rate modifier was examined in another test propellant formulation in comparison to the change in burning rate procured using ferric oxide as a burning rate modifier. Strand burning test procedures were used to test the formulations. The formulations used and the results obtained are as follows:

Component of Propellant Parts by Weight Composition Rb (at L000 p.s.i. Chamber Pressure) Ammonium perchlorate (coarse-about I80 52.00 Ammonium perchlorate (fine-about l2 l7.00 Aluminum powder 12-15 l4.00 Liquid Polybutadienelacrylic acid co olymer (having a carboxyl content of about 0.06 gr./ 100 gr. of olymer) l6.00 Burning Rate Modifier Fe,0,, L 0.26 Ferrous Ferrocene Monosulfonate l.00 0.50

When propellant compositions of the type disclosed in this example are stored at approximately 50 C. to +100 C. for relatively long periods of time no migration of the novel burning rate modifiers of the present invention occurs.

EXAMPLE 3 The change in burning rate arising at two combustion chamber pressures due to the use of ammonium ferrocene monosulfonate as a burning rate modifier and at two concentration levels, was examined in another propellant formulation. Strand burning test procedures were used to test these formulations. The formulations used and the results obtained are as follows:

Concentration of Propellant When propellant compositions of the type disclosed in this example are stored at approximately 50 C. to +100 C. for relatively long periods of time no migration of the novel burning rate modifiers of the present invention occurs.

lClaim:

l. A solid propellant composition based on a polymer selected from the group consisting of hydrocarbon, polysultide and urethane polymers and comprising, as a burning rate modifier component thereof, approximately I to 3 percent by weight of said composition of at least one salt of ferrocene monosulfonic acid which is less volatile than ferrocene.

2. A propellant composition as in claim 1 in which said polymer is a hydrocarbon polymer.

3. A propellant composition as in claim 2 in which said polymer is a copolymer of butadiene and acrylic acid.

4. A propellant composition as in claim I in which said salt of ferrocene monosulfonic acid is selected from the group consisting of the ammonium, sodium, ferrous, potassium, calcium, strontium and barium salts.

5. A propellant composition as in claim 4 in which is ammonium ferrocene monosulfonate.

6. A propellant composition as in claim 4 in which said salt is sodium ferrocene monosulfonate.

7. A propellant composition as in claim 4 in which said salt is ferrous ferrocene monosulfonate.

8. A process for modifying the burning rate of a SOild propellant composition based on a polymer selected from the group consisting of hydrocarbon, polysulfidc and urethane polymers which comprises incorporating in said composition, as a burning rate modifier component thereof, approximately 1 to 3 percent by weight of said propellant composition of at least one salt of ferrocene monosulfonic acid which is less volatile than ferrocene and burning said composition.

9. A process as in claim 8 in which said polymer is a hydrocarbon polymer.

10. A process as in claim 9 in which said polymer is a copolymer of butadiene and acrylic acid.

11. A process as in claim 8 in which said salt of ferrocenc monosulfonic acid which is less volatile than ferrocenc is selected from the group consisting of the ammonium, sodium, ferrous, potassium, calcium, strontium and barium salts.

12. A process as in claim 11 in which said salt is ammonium ferrocene monosulfonate.

13. A process as in claim 11 in which said salt is sodium lerrocene monosulfonate.

14. A process as in claim 11 in which said salt is ferrous ferrocene monosulfonate.

15. A process for preventing the migration of the burning rate modifier componentof a solid propellant composition based on a polymer selected from the group consisting of hydrocarbon, polysulfide and urethane polymers during the storage of said propellant composition which comprises incorporating in said propellant composition as said burning rate modifier component approximately 1 to 3 percent by weight of said propellant composition of at least one salt of ferrocene monosulfonic acid which is less volatile than ferroccne and storing said propellant composition.

16. A process as in claim 15 in which said polymer is a hydrocarbon polymer.

17. A process as in claim 16 in which said polymer is a copolymer of butadiene and acrylic acid.

18. A process as in claim 15 in which said salt of ferrocene monosulfonic acid which is less volatile than fcrroccne is selected from the group consisting of the ammonium, sodium, ferrous, potassium, calcium, strontium and barium salts.

19. A process as in claim 18 in which said salt is ammonium ferrocene monosulfonate.

20. A process as in claim 18 in which said salt is sodium ferrocene monosulfonate.

21. A process as in claim 18 in which said salt is ferrous fcrrocene monosulfonate.

22. A process as in claim 15 in which said propellant composition is stored at a temperature between approximately 50C. to+l00C.

said salt 

1. A SOLID PROPELLANT COMPOSITION BASED ON POLYMER SELECTED FROM THE GROUP CONSISTING OF HYDROCARBON, POLYSULFIDE AND URETHANE POLYMERS AND COMPRISING, AS A BURNING RATE MODIFIER COMPONENT THEREOF, APPROXIMATELY 1 TO 3 PERCENT BY WEIGHT OF SAID COMPOSITION OF AT LEAST ONE SALT OF FERROCENE MONOSULFONIC ACID WHICH IS LESS VOLATILE THAN FERROCENE.
 2. A propellant composition as in claim 1 in which said polymer is a hydrocarbon polymer.
 3. A propellant composition as in claim 2 in which said polymer is a copolymer of butadiene and acrylic acid.
 4. A propellant composition as in claim 1 in which said salt of ferrocene monosulfonic acid is selected from the group consisting of the ammonium, sodium, ferrous, potassium, calcium, strontium and barium salts.
 5. A propellant composition as in claim 4 in which said salt is ammonium ferrocene monosulfonate.
 6. A propellant composition as in claim 4 in which said salt is sodium ferrocene monosulfonate.
 7. A propellant composition as in claim 4 in which said salt is ferrous ferrocene monosulfonate.
 8. A process for modifying the burning rate of a solid propellant composition based on a poLymer selected from the group consisting of hydrocarbon, polysulfide and urethane polymers which comprises incorporating in said composition, as a burning rate modifier component thereof, approximately 1 to 3 percent by weight of said propellant composition of at least one salt of ferrocene monosulfonic acid which is less volatile than ferrocene and burning said composition.
 9. A process as in claim 8 in which said polymer is a hydrocarbon polymer.
 10. A process as in claim 9 in which said polymer is a copolymer of butadiene and acrylic acid.
 11. A process as in claim 8 in which said salt of ferrocene monosulfonic acid which is less volatile than ferrocene is selected from the group consisting of the ammonium, sodium, ferrous, potassium, calcium, strontium and barium salts.
 12. A process as in claim 11 in which said salt is ammonium ferrocene monosulfonate.
 13. A process as in claim 11 in which said salt is sodium ferrocene monosulfonate.
 14. A process as in claim 11 in which said salt is ferrous ferrocene monosulfonate.
 15. A process for preventing the migration of the burning rate modifier component of a solid propellant composition based on a polymer selected from the group consisting of hydrocarbon, polysulfide and urethane polymers during the storage of said propellant composition which comprises incorporating in said propellant composition as said burning rate modifier component approximately 1 to 3 percent by weight of said propellant composition of at least one salt of ferrocene monosulfonic acid which is less volatile than ferrocene and storing said propellant composition.
 16. A process as in claim 15 in which said polymer is a hydrocarbon polymer.
 17. A process as in claim 16 in which said polymer is a copolymer of butadiene and acrylic acid.
 18. A process as in claim 15 in which said salt of ferrocene monosulfonic acid which is less volatile than ferrocene is selected from the group consisting of the ammonium, sodium, ferrous, potassium, calcium, strontium and barium salts.
 19. A process as in claim 18 in which said salt is ammonium ferrocene monosulfonate.
 20. A process as in claim 18 in which said salt is sodium ferrocene monosulfonate.
 21. A process as in claim 18 in which said salt is ferrous ferrocene monosulfonate.
 22. A process as in claim 15 in which said propellant composition is stored at a temperature between approximately -50 * C. to +100 * C. 